Tubular support for tubular lamps



July 21, 1970 LA VERNE E. WALSH ET AL 3,521,112

TUBULAR SUPPORT FOR TUBULAR LAMPS Filed July 2, 1968 Inven'toT-s: Laverne E, WaLsh GeraLd W. Keimer by 01% f Their Aft T1169 United States Patent US. Cl. 313274 8 Claims ABSTRACT OF THE DISCLOSURE In a tubular incandescent lamp, a filament support of wire is formed with a transverse portion which loosely encircles the filament and also engages the envelope wall, for example a triangle or a spiral, and leg portions which extend in opposite directions from the transverse portion in longitudinal alignment with each other and longitudinally of the envelope. The support may be first inserted into the envelope, and the filament assembly may then be threaded into the envelope and through the support.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to electric incandescent lamps comprising a sealed envelope containing an incandescent filament. More particularly, the invention relates to filament support constructions.

Description of the prior art In recent years, there have appeared on the market incandescent lamps having tubular envelopes of rather small diameter and a coiled filament extending longitudinally of the envelope and supported therein by support members which are attached to the filament and which engage the inner envelope wall. Such supports include wire spiral members and sheet metal discs, and various wire shapes of varying degrees of complexity of design and difiiculty of assembly.

SUMMARY OF THE INVENTION It is an object of this invention to provide a novel form of filament support member which is particularly useful for miniaturized lamps having envelopes of quite small diameter, although it is not limited to such small lamps. It is also an object to provide a form of support which is self-supporting and is not attached to the filament coil, and which therefore avoids the problem of fastening the support to the filament coil, especially a coiled-coil.

In accordance with one aspect of the invention, the objects are attained by a filament support member of wire formed to provide a transverse portion located in a plane normal to the axis of the envelope and the filament, and having a part which loosely encircles the-filament and a part which is engageable with the envelope wall, and also including leg portions which extend in opposite directions from the transverse portion, in longitudinal alignment with each other and in longitudinal engagement with the envelope wall.

Further features and advantages of the invention will appear from the following detailed description of species thereof.

BRIEF DESCRIPTION OF THE DRAWING 3,521,112 Patented July 21, 1970 "Ice FIGS. 3 and 4 are a front and a side view, on an enlarged scale, of a modified form of the filament support which may be used in lamp envelopes of larger size;

FIGS. 5 and 6 are a front and a side view, on an enlarged scale, of a modification of the support shown in FIGS. 1 and 2; and

FIG. 7 is a side view of a lamp having another species of filament support in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Although not limited thereto, the invention is particularly useful in lamps of the compact tungsten-halogen cycle type now well known in the art, and the description will accordingly refer particularly to lamps of that type.

Referring to FIG. 1 of the drawing, the lamp illustrated therein comprises a tubular envelope 1 of vitreous material having a high softening point, preferably essentially fused silica. A helically coiled, preferably a coiledcoil, filament 2 of tungsten wire extends axially of the envelope and has single coiled legs 3 at its ends into which are fitted spud wires 4 which are welded to the ends of respective molybdenum foils 5 to which are also Welded the ends of respective outer lead wires 6. The said foils 5 are hermetically sealed in respective flattened pinch seals 7 at the ends of the envelope.

The envelope 1 is evacuated and filled with a suitable fill gas such as nitrogen, argon, krypton or xenon or mixtures thereof, and also a small amount of a halogen getter such as iodine or bromine or compounds thereof, by way of an exhaust tube, the tipped off residue of which is shown at 8.

In a lamp of watt, volt rating, by way of example, the envelope 1 may have an outside diameter of about one-quarter inch, and an internal length, between pinch seals 7, of about five-eighths inch or one inch, depending upon the physical parameters of the filament 2, such as coil diameter and pitch. During assembly of the lamp, the filament 2 is stretched and put in tension so that, when cold, its axis is quite straight; however, when heated, the filament coil may tend to bow downward toward the envelope wall. It is therefore desirable to provide a filament support which will prevent excessive bowing of the filament.

As shown in FIGS. 1 and 2, the filament support member 9 shown therein comprises a wire having an intermediate portion thereof formed as a triangle 10 in a plane normal to the axis of the envelope 1 and filament 2, and having leg portions 11 and 12 which extend in opposite directions from a vertex of the triangle 10 in longitudinal alignment with each other and in longitudinal engagement with the inner envelope wall to maintain the triangle in its transverse position. Preferably, one leg 11 is made long enough so that its end is embedded and anchored in one of the pinch seals 7 to positively prevent rotation of the support, and the other leg 12 may be made just long enough to prevent the support from tipping during assembly of the lamp.

It will be seen in FIG. 2 that the support 9 is of the non-contacting type wherein the triangular part 10 loosely encircles the filament 2 and has its vertices, and the legs 11 and 12, in engagement with the inner envelope sur face. During manufacture of the lamp, the support member 9 is first inserted in the envelope 1 which is at that time open at both ends, the support 10 being held in the envelope by frictional engagement with its inner walls. With the envelope in a vertical position, the filament assembly of filament 2, spuds 4, foils 5 and wires 6 is inserted down the tube and threaded through the triangular portion 10 of the support 9 before the pinch seals 7 are formed. An advantage of the triangular support is that it has a wide part, along one of its bases,

, 3 for the foil to pass through and yet is suificiently close to the filament coil 2 to afford support.

While the lamp illustrated in FIG. 1 has a support 9 with its transverse triangular portion at the longitudinal center of the filament coil, it will be evident that two supports 9 may be used, especially in a longer lamp, each support having one of its legs 11 anchored in respective pinch seals 7.

When using the triangular type support in lamps of larger diameter, it may be modified as shown in FIGS. 3 and 4 by forming extensions 14 at the vertices of the triangular transverse portion 10a of the support 9a which is otherwise like the support 9 of FIGS. 1 and 2, as indicated by the use of the same numerals with the addition of the letter a. It will be evident that the length of the extensions 14 is adjusted for the inside diameter of the envelope, and the size of the triangle 10a is adjusted for the outside diameter of the filament coil or the Width of the foil 5 (FIG. 1).

In FIGS. 5 and 6 the support 9b is modified by twisting together portions of the wire at the vertex from which extends the legs 11b and 12b. The triangular portion 10b is thereby firmly held together. Also, more spacing is provided between the filament coil (not shown) and the legs 11b and 12b of the support. On the other hand, the shape of the triangle 1% may be modified to center it about a filament coil which is in the axis of the envelope as it is in FIGS. 1 and .2. The length of the twisted portion 15 may also be varied for lamp envelopes of different diameters.

As seen clearly in FIG. 6, the legs 11b and 12b of the support member 91) are preferably inclined downwardly away from the transverse portion 1015, thus insuring a firm frictional contact of the support with the inside of the lamp envelope 1 (FIG. 1) when the support is inserted into the envelope. It will be evident that the legs 11 and 12 in FIG. 1, and legs 11a and 12a in FIG. 4, may be similarly inclined.

The lamp shown in FIG. 1 may be generally similar to that shown in FIG. 1 as indicated by the numbering of similar parts with the same numeral except for the addition of the letter c. In this case, the transverse portion 10c of the filament support member is of spiral form with its innermost turn of a size to loosely encircle the filament 2c, and its outermost turn engageable with the inner wall of the envelope 1c. The leg portion 12c extends from the outer turn of the spiral portion 100 longitudinally of the envelope, and is doubled back upon itself to extend toward and beyond the transverse spiral portion 100 to form the leg 110. In this case, neither leg 110 or 12c is anchored in a pinch seal 70 but the said legs extend close to the said pinch seals at respective ends of the inner envelope. In this case, the filament coil is mounted with its axis slightly to one side of the axis of the envelope. This may be desirable in some cases to increase the spacing between the filament 2c and the legs 11c and 120 of the support, and thereby decrease likelihood of arcing between the said filament and legs. which may otherwise occur under a particular combination of certain conditions such as operating voltage, filament length, type of gas filling, etc.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An electric lamp comprising a tubular envelope,

a helical coiled filament extending longitudinally of the envelope, a filament support member of wire formed with a transverse portion located in a plane normal to the envelope axis and including a part loosely encircling the filament coil and a part engageable with the inner envelope wall at least at several points around its circumference sufiicient in number and extent to fix the position of said transverse member, said filament support member also including leg portions which extend in opposite directions from said transverse portion in longitudinal alignment with each other and in longitudinal engagement with said inner envelope wall and which maintain said transverse portion in said plane normal to the envelope axis.

2. A lamp as set forth in claim 1 wherein the said transverse portion of the filament support member is of triangular shape and said leg portions extend therefrom at one of its vertices.

3. A lamp as set forth in claim 2 wherein the triangular transverse portion of the filament support member has extensions at its vertices and in said plane normal to the envelope axis for engagement with the envelope wall.

4. A lamp as set forth in claim 2 and having a pinch seal at least at one end thereof with a lead-in conductor extending through said seal to the filament, and wherein one of the said leg portions of the support member has its terminal end portion embedded and anchored in said pinch seal.

5. A lamp as set forth in claim 2 wherein the portions of wire at said one of the vertices of the transverse triangular portion of the support member are twisted together.

6. A lamp as set forth in claim 5 wherein the longitudinally aligned leg portions of the support member are inclined downwardly away from the transverse triangular portion whereby to serve also as spring members holding the triangular portion against the envelope walls.

7. A lamp as set forth in claim 1 wherein the said transverse portion of the filament support member is of spiral shape with an opening at its center encircling the filament, and its leg portions are of wire which extends first in one direction from the outer periphery of the spiral and is bent back upon itself to extend toward and beyond the spiral in the opposite direction.

8. A lamp as set forth in claim 1 and having a pinch seal at least at one end thereof with a lead-in conductor extending through said seal to the filament, and wherein one of the said leg portions of the support member has its terminal end portion embedded and anchored in said pinch seal.

References Cited UNITED STATES PATENTS 923,797 6/1909 McNeill 3 l3274 2,064,490 l2/1936 Nobel 313-274 2,910,605 10/1959 Hodge 313-274 X 3,173,051 3/1965 Berlinghof et al. 313274 3,211,941 10/1965 Sanden et al 313274 X 3,390,299 6/1968 Van Sickler et al. 313--274 FOREIGN PATENTS 1,110,928 4/1968 Great Britain.

JOHN W. HUCKERT, Primary Examiner A. J. JAMES, Assistant Examiner US. Cl. X.R. 

